Carl Sagan

Carl Sagan

Carl Edward Sagan (/ˈseɪɡən/; November 9, 1934 – December 20, 1996) was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and other natural sciences. His contributions were central to the discovery of the high surface temperatures of Venus. However, he is best known for his contributions to the scientific research of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages that were sent into space: the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them.

He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. Sagan is known for many of his popular science books, such as The Dragons of Eden, Broca’s Brain and Pale Blue Dot, and for the award-winning 1980 television series Cosmos: A Personal Voyage, which he narrated and co-wrote. The most widely watched series in the history of American public television, Cosmos has been seen by at least 500 million people across 60 different countries. The book Cosmos was published to accompany the series. He also wrote the science fiction novel Contact, the basis for a 1997 film of the same name.

Sagan always advocated scientific skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI). He spent most of his career as a professor of astronomy at Cornell University where he directed the Laboratory for Planetary Studies. Sagan and his works received numerous awards and honors, including the NASA Distinguished Public Service Medal, the National Academy of Sciences Public Welfare Medal, the Pulitzer Prize for General Non-Fiction for his book The Dragons of Eden, and, regarding Cosmos: A Personal Voyage, two Emmy Awards, the Peabody Award and the Hugo Award. He married three times and had five children. After suffering from myelodysplasia, Sagan died of pneumonia at the age of 62 on December 20, 1996.

Education and scientific career

He attended the University of Chicago, where he participated in the Ryerson Astronomical Society, received a bachelor of arts in self-proclaimed “nothing” with general and special honors in 1954, a bachelor of science in physics in 1955, and a master of science in physics in 1956 before earning a PhD in astronomy and astrophysics in 1960.During his time as an honors program undergraduate, Sagan worked in the laboratory of the geneticist H. J. Muller and wrote a thesis on the origins of life with physical chemist H. C. Urey. He used the summer months of his graduate studies to work with planetary scientist Gerard Kuiper (thesis advisor), physicist George Gamow, and chemist Melvin Calvin. From 1960 to 1962 Sagan was a Miller Fellow at the University of California, Berkeley. From 1962 to 1968, he worked at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. At the same time, he worked with geneticist Joshua Lederberg.

Sagan lectured and did research at Harvard University until 1968, when he moved to Cornell University in Ithaca, New York, after being denied tenure at Harvard. It has been suggested that Sagan was denied tenure in part because of his publicised scientific advocacy, which some scientists perceived as being self-promotion. He became a full professor at Cornell in 1971, and directed the Laboratory for Planetary Studies there. From 1972 to 1981, Sagan was associate director of the Center for Radiophysics and Space Research (CRSR) at Cornell.

Sagan was associated with the U.S. space program from its inception. From the 1950s onward, he worked as an advisor to NASA, where one of his duties included briefing the Apollo astronauts before their flights to the Moon. Sagan contributed to many of the robotic spacecraft missions that explored the Solar System, arranging experiments on many of the expeditions. He conceived the idea of adding an unalterable and universal message on spacecraft destined to leave the Solar System that could potentially be understood by any extraterrestrial intelligence that might find it. Sagan assembled the first physical message that was sent into space: a gold-anodized plaque, attached to the space probe Pioneer 10, launched in 1972. Pioneer 11, also carrying another copy of the plaque, was launched the following year. He continued to refine his designs; the most elaborate message he helped to develop and assemble was the Voyager Golden Record that was sent out with the Voyager space probes in 1977. Sagan often challenged the decisions to fund the Space Shuttle and the International Space Station at the expense of further robotic missions.

Sagan taught a course on critical thinking at Cornell University until he died in 1996 from pneumonia, a few months after finding that he was in remission of myelodysplastic syndrome.

Scientific achievements

Former student David Morrison describes Sagan as “an ‘idea person’ and a master of intuitive physical arguments and ‘back of the envelope’ calculations,” and Gerard Kuiper said that “Some persons work best in specializing on a major program in the laboratory; others are best in liaison between sciences. Dr. Sagan belongs in the latter group.”

Sagan’s contributions were central to the discovery of the high surface temperatures of the planet Venus. In the early 1960s no one knew for certain the basic conditions of that planet’s surface, and Sagan listed the possibilities in a report later depicted for popularization in a Time–Life book, Planets. His own view was that Venus was dry and very hot as opposed to the balmy paradise others had imagined. He had investigated radio emissions from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA’s Jet Propulsion Laboratory, he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his conclusions on the surface conditions of Venus in 1962.

Sagan was among the first to hypothesize that Saturn’s moon Titan might possess oceans of liquid compounds on its surface and that Jupiter’s moon Europa might possess subsurface oceans of water. This would make Europa potentially habitable. Europa’s subsurface ocean of water was later indirectly confirmed by the spacecraft Galileo. The mystery of Titan’s reddish haze was also solved with Sagan’s help. The reddish haze was revealed to be due to complex organic molecules constantly raining down onto Titan’s surface.

He further contributed insights regarding the atmospheres of Venus and Jupiter as well as seasonal changes on Mars. He also perceived global warming as a growing, man-made danger and likened it to the natural development of Venus into a hot, life-hostile planet through a kind of runaway greenhouse effect. Sagan and his Cornell colleague Edwin Ernest Salpeter speculated about life in Jupiter’s clouds, given the planet’s dense atmospheric composition rich in organic molecules. He studied the observed color variations on Mars’ surface and concluded that they were not seasonal or vegetational changes as most believed but shifts in surface dust caused by windstorms.

Sagan is best known, however, for his research on the possibilities of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.

He is also the 1994 recipient of the Public Welfare Medal, the highest award of the National Academy of Sciences for “distinguished contributions in the application of science to the public welfare”. He was denied membership in the Academy, reportedly because his media activities made him unpopular with many other scientists.

Scientific and critical thinking advocacy

Sagan’s ability to convey his ideas allowed many people to understand the cosmos better—simultaneously emphasizing the value and worthiness of the human race, and the relative insignificance of the Earth in comparison to the Universe. He delivered the 1977 series of Royal Institution Christmas Lectures in London. He hosted and, with Ann Druyan, co-wrote and co-produced the highly popular thirteen-part Public Broadcasting Service (PBS) television series Cosmos: A Personal Voyage.

Cosmos covered a wide range of scientific subjects including the origin of life and a perspective of our place in the Universe. The series was first broadcast by the PBS in 1980, winning an Emmy and a Peabody Award. It has been broadcast in more than 60 countries and seen by over 500 million people,making it the most widely watched PBS program in history. In addition, Time magazine ran a cover story about Sagan soon after the show broadcast, referring to him as “creator, chief writer and host-narrator of the new public television series Cosmos, [and] takes the controls of his fantasy spaceship”. However, Sagan was criticised for putting too much attention into the series, with several of his classes at Cornell being cancelled and complaints from his colleagues.

Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen with radio telescopes for signals from potential intelligent extraterrestrial life-forms. Sagan was so persuasive that by 1982 he was able to get a petition advocating SETI published in the journal Science and signed by 70 scientists including seven Nobel Prize winners. This was a tremendous increase in the respectability of this controversial field. Sagan also helped Frank Drake write the Arecibo message, a radio message beamed into space from the Arecibo radio telescope on November 16, 1974, aimed at informing potential extraterrestrials about Earth.

Sagan was chief technology officer of the professional planetary research journal Icarus for twelve years. He co-founded The Planetary Society, the largest space-interest group in the world, with over 100,000 members in more than 149 countries, and was a member of the SETI Institute Board of Trustees. Sagan served as Chairman of the Division for Planetary Science of the American Astronomical Society, as President of the Planetology Section of the American Geophysical Union, and as Chairman of the Astronomy Section of the American Association for the Advancement of Science (AAAS).

At the height of the Cold War, Sagan became involved in public awareness efforts for the effects of nuclear war when a mathematical climate model suggested that a substantial nuclear exchange could upset the delicate balance of life on Earth. He was one of five authors – the “S” – of the “TTAPS” report, as the research paper came to be known. He eventually co-authored the scientific paper hypothesizing a global nuclear winter following nuclear war. He also co-authored the book A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, a comprehensive examination of the phenomenon of nuclear winter.

Sagan also wrote books to popularize science, such as Cosmos, which reflected and expanded upon some of the themes of A Personal Voyage and became the best-selling science book ever published in English; The Dragons of Eden: Speculations on the Evolution of Human Intelligence, which won a Pulitzer Prize; and Broca’s Brain: Reflections on the Romance of Science. Sagan also wrote the best-selling science fiction novel Contact in 1985, based on a film treatment he wrote with his wife in 1979, but he did not live to see the book’s 1997 motion picture adaptation, which starred Jodie Foster and won the 1998 Hugo Award for Best Dramatic Presentation.

He wrote a sequel to Cosmos, Pale Blue Dot: A Vision of the Human Future in Space, which was selected as a notable book of 1995 by The New York Times. He appeared on PBS’ Charlie Rose program in January 1995. Sagan also wrote the introduction for Stephen Hawking’s bestseller, A Brief History of Time. Sagan was also known for his popularization of science, his efforts to increase scientific understanding among the general public, and his positions in favor of scientific skepticism and against pseudoscience, such as his debunking of the Betty and Barney Hill abduction. To mark the tenth anniversary of Sagan’s death, David Morrison, a former student of Sagan’s, recalled “Sagan’s immense contributions to planetary research, the public understanding of science, and the skeptical movement” in Skeptical Inquirer.

Sagan hypothesized in January 1991 that enough smoke from the 1991 Kuwaiti oil fires “might get so high as to disrupt agriculture in much of South Asia …” He later conceded in The Demon-Haunted World that this prediction did not turn out to be correct: “it was pitch black at noon and temperatures dropped 4°–6 °C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared”. A 2007 study noted that modern computer models have been applied to the Kuwait oil fires, finding that individual smoke plumes are not able to loft smoke into the stratosphere, but that smoke from fires covering a large area, like some forest fires or the burning of cities that would be expected to follow a nuclear strike, would loft significant amounts of smoke into the stratosphere.

In his later years Sagan advocated the creation of an organized search for near-Earth objects that might impact the Earth. When others suggested creating large nuclear bombs that could be used to alter the orbit of a NEO that was predicted to hit the Earth, Sagan proposed the Deflection Dilemma: If we create the ability to deflect an asteroid away from the Earth, then we also create the ability to deflect an asteroid towards the Earth—providing an evil power with a true doomsday bomb. His interest in the use of nuclear weapons in space grew out of his work in 1958 for the Armour Research Foundation’s Project A119, concerning the possibility of detonating a nuclear device on the Lunar surface.

Sagan was a critic of Plato. Sagan said of Plato: “Science and mathematics were to be removed from the hands of the merchants and the artisans. This tendency found its most effective advocate in a follower of Pythagoras named Plato.” and “He (Plato) believed that ideas were far more real than the natural world. He advised the astronomers not to waste their time observing the stars and planets. It was better, he believed, just to think about them. Plato expressed hostility to observation and experiment. He taught contempt for the real world and disdain for the practical application of scientific knowledge. Plato’s followers succeeded in extinguishing the light of science and experiment that had been kindled by Democritus and the other Ionians.”

Popularizing science

Speaking about his activities in popularizing science, Sagan said that there were at least two reasons for scientists to explain what science is about. Naked self-interest was one because much of the funding for science came from the public, and the public had a right to know how their money was being spent. If scientists increased public excitement about science, there was a good chance of having more public supporters. The other reason was the excitement of communicating one’s own excitement about science to others.